Comment 7 for bug 1907421

------- Comment From <email address hidden> 2021-01-20 10:02 EDT-------
re: backporting of the qemu patches... I was planning to open a separate bug for this once we determined whether the kernel fix would actually get integrated into focal/groovy.

The primary difference from 5.2 and focal/groovy would be the state of the qemu build system as it went through some recent changes, so there may be some accomodation required to backport. The list you provided is mostly accurate. We can definitely skip:
84567ea763 update-linux-headers: Add vfio_zdev.h
as this is for a different feature that integrated in the same pull request, not part of this bugfix

And we might also be able to skip:
408b55db8b s390x/pci: Move header files to include/hw/s390x
but this would require a minor header change to an include statment.

Testing for the kernel alone is tricky (you need to create a vfio-pci device and then issue the VFIO_IOMMU_GET_INFO ioctl and validate that the DMA limit is included in the response -- I've used a custom QEMU build to do that). Creating a test when both kernel and QEMU changes are available is much easier (but does still require special PCI hardware like a mellanox adapter to pass through to the guest).